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While reading the following Wikipedia section about Carnitine, it occurred to me this is a valid reason for fasted cardio being more effective at fat burning calories in the short run.
Two things:
Summary: Carnitine helps move fatty acids into mitochondria to be used as energy. The liver inhibits this step when it’s in the process of storing excess sugar. So maybe it’s not just fasted cardio but also cardio during normal blood sugar levels that’s effective where cardio during excessive sugar has fatty acid metabolism slowed down.
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From Wikipedia:
Regulation of fatty acid β oxidation
The carnitine-mediated entry process is a rate-limiting factor for fatty acid oxidation and is an important point of regulation.
Inhibition
The liver starts actively making triglycerides from excess glucose when it is supplied with glucose that cannot be oxidized or stored as glycogen. This increases the concentration of malonyl-CoA, the first intermediate in fatty acid synthesis, leading to the inhibition of carnitine acyltransferase 1, thereby preventing fatty acid entry into the mitochondrial matrix for β oxidation. This inhibition prevents fatty acid breakdown while synthesis is happening.
Activation
Carnitine activation occurs due to a need for fatty acid oxidation which is required for energy production. During vigorous muscle contraction or during fasting, ATP concentration decrease and AMP concentration increase which leads to the activation of AMP-activated protein kinase (AMPK). AMPK phosphorylates acetyl-CoA carboxylase which catalyzes malonyl-CoA synthesis. This phosphorylation inhibits the acetyl-CoA carboxylase which in turn lowers the concentration of malonyl-CoA and as a result it relieves the inhibition of fatty acyl–carnitine transport into mitochondria, thus allowing β oxidation to replenish the supply of ATP.
Two things:
- We make enough from all the lysine we get in our protein - no need to supplement
- Calories in/out says this might be more efficient at burning fat but the energy used during the day would have rebalanced the fat anyway.
Summary: Carnitine helps move fatty acids into mitochondria to be used as energy. The liver inhibits this step when it’s in the process of storing excess sugar. So maybe it’s not just fasted cardio but also cardio during normal blood sugar levels that’s effective where cardio during excessive sugar has fatty acid metabolism slowed down.
===============================
From Wikipedia:
Regulation of fatty acid β oxidation
The carnitine-mediated entry process is a rate-limiting factor for fatty acid oxidation and is an important point of regulation.
Inhibition
The liver starts actively making triglycerides from excess glucose when it is supplied with glucose that cannot be oxidized or stored as glycogen. This increases the concentration of malonyl-CoA, the first intermediate in fatty acid synthesis, leading to the inhibition of carnitine acyltransferase 1, thereby preventing fatty acid entry into the mitochondrial matrix for β oxidation. This inhibition prevents fatty acid breakdown while synthesis is happening.
Activation
Carnitine activation occurs due to a need for fatty acid oxidation which is required for energy production. During vigorous muscle contraction or during fasting, ATP concentration decrease and AMP concentration increase which leads to the activation of AMP-activated protein kinase (AMPK). AMPK phosphorylates acetyl-CoA carboxylase which catalyzes malonyl-CoA synthesis. This phosphorylation inhibits the acetyl-CoA carboxylase which in turn lowers the concentration of malonyl-CoA and as a result it relieves the inhibition of fatty acyl–carnitine transport into mitochondria, thus allowing β oxidation to replenish the supply of ATP.
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